1. Field of the Invention
The invention relates to a failure diagnosis system, and a vehicle-mounted ECU for use in the failure diagnosis system.
2. Description of the Related Art
There is a known technology in which when an erasure request on diagnostic information is received from a failure diagnosis device that is connected to a vehicle from the outside of the vehicle, the diagnostic information in a master CPU is erased, and then the erasure request is also output to other CPUs (e.g., see Japanese Patent No. 3203884).
Recently, the CARB OBD2 regulations were revised (December, 2007) (described in detail in conjunction with embodiments of the invention), requiring a process of erasing diagnostic information at the time of writing a vehicle identification number (VIN). The erasure of diagnostic information needs to be substantially the same as the erasure of diagnostic information that is requested by a scan tool, and if the diagnostic information is not erased, the VIN writing must not be executed.
However, along with the recent trend toward multi-functions of a vehicle system, the number of ECUs employed in the system is increasing, and there are cases where, besides the ECU that retains the VIN, there also exists another ECU that retains diagnostic information that needs to be erased at the time of writing the VIN. In such a case, the other ECU do not have a measure for knowing that an ECU retaining the VIN was subjected to the writing of the VIN, and therefore there is a risk that the diagnostic information of the other ECU may remain.